1. Field of the Invention
The present invention relates generally to a hair iron which applies heat to hair to create a variety of hairstyles and, more particularly, to a hair iron which is widely used as a tool for setting hair in a general beauty shop or home.
2. Description of the Related Art
Generally, a hair iron is divided into upper and lower casings to allow hair to be inserted between the upper and lower casings. The upper and lower casings are connected at first ends thereof to each other by a hinge structure so that the upper and lower casings rotate at a predetermined angle, thus allowing the upper and lower casings to come into close contact with each other or to move away from each other.
Either or each of the upper and lower casings is provided with a heat generating unit to apply heat to the hair. For example, the heat generating unit may include a hot plate which is in direct contact with hair, a heater which generates heat to supply the heat to the hot plate, and a power supply circuit unit which supplies power to the heater. Thus, when power is applied from the power supply circuit unit to the heater, the heater generates heat and heats the hot plate. Thereby, heat and pressure are applied to hair which is placed between the upper and lower casings, so that a hairstyle can be changed.
Meanwhile, in the hinge structure enabling the upper and lower casings to come into close contact with each other and move away from each other at a predetermined angle, hinge holes formed in the first ends of the upper and lower casings are aligned with each other, and thereafter a hinge shaft is fitted into the hinge holes. Further, an elastic member, including a torsion spring or a plate spring, is installed between the upper and lower casings, so that both ends of the elastic member are supported, respectively, by the upper and lower casings. Thus, when force is exerted on the upper and lower casings to put them in contact with each other, so that both the heat generating units come into contact with each other, the elastic member is elastically compressed. Meanwhile, when the force is removed from the upper and lower casings, the upper and lower casings move away from each other by the elastic restoring force of the elastic member.
However, the conventional hinge structure requires a construction for preventing the hinge shaft from being removed from the hinge holes of the upper and lower casings, after the hinge shaft has been fitted into the hinge holes. For example, a locking screw having a head which is larger than the hinge hole is fastened to each of the opposite ends of the hinge shaft, or a locking ring which has an outer diameter larger than the hinge hole is provided on each end of the hinge shaft.
Thus, when the hinge structure of the upper and lower casings is assembled or disassembled, the locking screw or the locking ring must be fastened to or unfastened from each end of the hinge shaft, so that it is very complicated and takes a long time to perform the assembly or disassembly operation. As for the locking screw, it is fastened in the same direction as the rotating direction of the hinge structure, so that the locking screw gradually becomes loosened by repeated rotations of the upper and lower casings. Meanwhile, as for the locking ring, the undesirable loosening of the locking ring is prevented, but it is more difficult to connect or disconnect the locking ring to or from the hinge shaft.
Further, in order to connect the locking screw or the locking ring to each of the opposite ends of the hinge shaft, the assembly or disassembly operation must be performed at both sides of the upper and lower casings, so that a coupled part is exposed to the outside, and thus the appearance is poor. Therefore, the coupled part is covered with an additional cover member, and the cover member makes the assembly and disassembly operation of the hinge structure more complicated. In addition, a structure for coupling the cover member to the upper and lower casings is required, so that the hinge coupled part of the upper and lower casings becomes more sophisticated, and thus it is difficult to manufacture a mold and cost is increased.
Further, the conventional hair iron is problematic in that there is heat loss resulting from the transfer of heat from the heat generating unit to the upper and lower casings, and besides, heat is not reliably transferred if a gap is formed between the heater and the hot plate of the heat generating unit, so that thermal efficiency is low.